1. Field of the Invention
The invention relates to a hybrid high-voltage or medium-voltage switch device. The qualifier “hybrid” applies to the breaking action, which is of a mixed type in which two different breaking techniques cooperate. In particular, a switch device is qualified as a hybrid device if it includes a vacuum switch closing a first pair of arc contacts and further includes a gas switch comprising a second pair of arc contacts.
2. Description of the Prior Art
A device of the above type is disclosed in U.S. Pat. No. 3,038,980. It comprises an enclosure filled with a dielectric gas and having a longitudinal axis; the two switches are disposed inside the enclosure and electrically connected in series; the operating mechanism of the device is disposed outside the enclosure. The mechanism for actuating the contacts of the two switches is relatively simple, in the sense that one of the two contacts of the gas switch is attached to an adjacent mobile contact in the vacuum switch. The other contact of the gas switch is attached to an operating rod connected to the operating mechanism of the device. A spring mechanism associated with an abutment holds the contacts of the gas switch together over a first portion of their travel when the device is opened, until the contacts of the vacuum switch are separated by a particular distance. The object of this kind of sequence for separating the contacts of the two pairs is to be able to delay the separation of the contacts of the second pair (those of the gas switch) relative to those of the first pair (those of the vacuum switch).
However, the above kind of sequence is not satisfactory if the hybrid high-voltage breaker device combines a gas switch for a standard high voltage greater than 72.5 kV with a vacuum switch for a standard medium voltage less than 52 kV. In effect, as long as the contacts of the gas switch are not separated during the process of breaking a fault current by the device, the vacuum switch withstands all of the transient remaking voltage at the terminals of the breaker device during the separation of its contacts. Now, the vacuum switch is adapted only to withstand a remaking voltage which remains within the limits of the medium voltage. Accordingly, a high-voltage hybrid breaker device using the sequence described hereinabove to separate the contacts could break the current only after the separation of the two contacts of the gas switch. This operation implies a relatively long arcing time, which a vacuum switch is not designed to withstand. The general structure of the device described in U.S. Pat. No. 3,038,980 has no provision for modifying the sequence for separating the contacts. In particular, with the above kind of device it is not possible to obtain simultaneous or delayed separation of the contacts of the vacuum switch relative to separation of the contacts of the gas switch.
The patent application EP1109187 discloses another device of the above type, in which the contact separation sequence can be adjusted to obtain simultaneous or slightly delayed separation of the contacts of the vacuum switch relative to separation of the contacts of the gas switch. The mobile contact of the vacuum switch is connected to a link, one end of which is mobile in rotation, this end of the link, also known as the head of the link, being articulated to a crank of a flywheel that can be coupled to or decoupled from a toothed rod driven in translation by the operating rod of the gas switch.
The above device has some disadvantages from a mechanical point of view, however. First of all, it is necessary to exert a sufficient force on the mobile contact of the vacuum switch for as long as current is allowed to flow, in order to have a mutual pressure between the bearing surfaces of the contacts of this switch which is greater than a specified value, in order to resist electrodynamic forces while the current is flowing. The flywheel of the device must therefore be provided with a return spring system for exerting the required force on the mobile contact of the vacuum switch. On the other hand, the transmission of the movement from the operating rod of the gas switch to the vacuum switch is effected by means of a link whose axis is oblique to the axis of movement in translation of the mobile contact of the vacuum switch. This results in high transverse stresses on the vacuum switch, which can limit is mechanical durability.
Finally, the patent application EP1117114 describes another device of the above type which has the advantage over the preceding device that the mobile contact of the vacuum switch is always subjected to forces directed only in the direction of the longitudinal axis of the switch. Moreover, spring means are provided to maintain a mutual pressure between the contacts of the vacuum switch for as long as that switch is closed. However, the separation movement of the contacts of the vacuum switch is driven by the operating rod of the gas switch, with the result that the contacts of the vacuum switch must not separate until opening of the contacts of the gas switch is completed. The above device must have this kind of deferred contact separation sequence in order to cause a zero-crossing of the current before the vacuum switch alone breaks the current. In effect, the device is used exclusively as a generator circuit-breaker, and the gas switch is consequently present only to reduce the percentage asymmetry of the current.
It is obviously not possible with the above device to achieve simultaneous or slightly delayed separation of the contacts of the vacuum switch relative to separation of the contacts of the gas switch.
The invention aims first of all to remedy the disadvantages or limitations of the prior art techniques by proposing a high-voltage or medium-voltage hybrid breaker device that is relatively compact and durable and which, whilst operating with a single operating member, i.e. with an operating mechanism connected to only one operating rod, makes provision for adjusting the contact separation sequence of the switches in order to distribute adequately between the vacuum switch and the gas switch the transient remaking voltage that appears between the contacts of each switch as soon as they separate. The invention achieves the above objective by proposing a breaker device operating on the principle of the hybrid breaker device described in European patent application EP1271590A1 published on Jan. 2, 2003. The invention thereafter aims to prevent any bouncing movement of the mobile contact of the vacuum switch when a current is interrupted by the device, in order to prevent further arcing in the switch.